I grant you the Ferdinand ban was excessive, but as it was unprecedented I don't think we have anything before or since to compare it to. While biting is unusual we do have a precedent which only resulted in a yellow card. Additionally we have plenty of cases of Violent conduct, but very few that are punished at 3 times the standard sanction.
But on the repeat offender charge I've asked this question of Robert, but don't understand the logic. The FA is supposed to only take into consideration things within its own jurisdiction, so with everything you've quoted other tan the racial abuse happening either under FIFA jurisdiction or another league, I'm not sure why they are being considered. Put it this way would you accept the FA doubling or tripling a ban on Rooney or any other player because they've in the past received sanction on international duty?
I get that many don't seem to like Suarez, and while I might be bias in this area I do think its fair that perception of unlikeability is what drives much of the desire to single him out. Yes other players dive, foul, cheat, punch (although few bite) some within a single season, let alone 3, yet they don't receive near the venom aimed at Suarez by the press or opposing fans.